The invention relates generally to fluid turbine blades and more particularly, to a fluid turbine blade including a circular spar.
Commonly, fluid turbines are employed to generate electricity from kinetic energy of fluids. Two non-limiting turbine examples include wind energy and marine hydrokinetic energy turbines. Such turbines include three major components: a structural support component, a generator component and a rotor component. The rotor component further includes turbine blades that are employed to convert the kinetic energy of fluid to a mechanical energy. Furthermore, the mechanical energy is converted to electricity with the help of the generator component.
Typically, wind turbine blades, for example, include a rectangular or I shaped spar disposed along a span of the wind turbine blade. The spar carries a major portion of a load induced by the kinetic energy of the wind on the wind turbine blade. The load is directed at an angle on the wind turbine blade and results in a multiaxial loading of the rectangular or I shaped spar. The multiaxial state of loading including flapwise bending, edgewise bending and torsion, induces warping of the rectangular or I-shaped spar and results in higher stresses in the rectangular or I shaped spar. Therefore, the multiaxial state of loading leads to an inefficient design and excess material utilization. The excess material utilization results in a heavier wind turbine blade. Furthermore, the inefficient design increases the maintenance cost and reduces life of the wind turbine blade
Advanced aeroelastic axial-twist coupling is seen as a way to shed the multiaxial load and a control mechanism. The wind turbine blades with rectangular or I-beam spars are not conducive for inducing the axial twist coupling and results in a more complicated aerodynamic shape to achieve axial twist coupling. The complicated shapes lead to increased cost of manufacturing and design complexity.
Hence, there is a need for an improved fluid turbine blade design to address one or more aforementioned issues.